panfrost: Add panfrost_bo_{alloc,free}()

panfrost: Add panfrost_bo_{alloc,free}()

Thanks to that we avoid the recursive call into panfrost_bo_create()
and we can get rid of panfrost_bo_release() by inlining the code in
panfrost_bo_unreference().

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>